The present invention generally relates to semiconductor analog and logic circuits, and more particularly to a method of suppressing noise up-conversion mechanisms in inductor-capacitor (LC) oscillators.
Typically, near-carrier phase noise in complementary metal-oxide semiconductors (CMOS) LC oscillators is dominated by noise generated at low frequencies, and up-converted to frequencies around the carrier by non-linear effects within the oscillator. In CMOS the type of noise source that typically dominates is flicker noise. Flicker noise is a type of electronic noise, generated by most electronics devices, having a 1/f power spectral density, i.e., the power spectral density of the noise is inversely proportional to the frequency. CMOS devices including sub-micron feature sizes can generate substantial flicker noise (also referred to as “1/f noise”) at frequencies up to a few Megahertz or more. While the signals generated by the oscillator of interest are typically much higher (in the GHz range), the up-conversion mechanisms within the oscillator result in the low frequency flicker noise being up-converted, and dominating the noise profile at frequencies close to the carrier.